Make sure the contents of the WWW-Authenticate header is

Make sure the contents of the WWW-Authenticate header is
passed on a 4xx error by proxy. Previously all headers
were dropped, resulting in the browser being unable to
authenticate.
PR:
Obtained from:
Submitted by:	Dr Richard Reiner <rreiner@fscinternet.com>, Richard Danielli <rdanielli@fscinternet.com>, Graham Wiseman <gwiseman@fscinternet.com>, David Henderson <dhenderson@fscinternet.com>
Reviewed by:	Graham Leggett

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96982 13f79535-47bb-0310-9956-ffa450edef68